1. Field of the Invention
The present invention relates to desensitizer compositions. In greater detail, it relates to desensitizer compositions which reduce or extinguish the function of developers of coloring colorless couplers.
2. Description of the Prior Art
It is known that a developed color image can be formed by the contact reaction between an electron donating or proton accepting colorless organic compound (hereinafter, called a coupler) and an electron accepting or proton donating solid acid (hereinafter called a developer). This phenomenon has been utilized in pressure-sensitive copying papers (for example, as described in U.S. Pat. Nos. 2,505,470, 2,505,489, 2,550,471, 2,548,366, 2,712,507, 2,730,456, 2,730,457, 3,418,250 and 3,672,935) and in heat-sensitive recording papers (for example, as described in Japanese Patent Publications Nos. 4160/68, 7600/68 and 14039/70 and U.S. Pat. No. 2,939,090).
A printing process is also known which comprises forming a color image by supplying a coupler containing ink to a sheet having a developer layer coated thereon (as described in German Patent Application (OLS) No. 1,939,962).
Examples of developer include clays, phenol resins, metal salts of aromatic carboxylic acids, etc.
In general, the developer is uniformly applied to the total surface of a support. Accordingly, it is the general case that a process for desensitizing comprises applying a desensitizer containing composition to areas which are not to be recorded by means of a printing press, etc. As desensitizers, organic amines or quaternary salts thereof (see U.S. Pat. No. 2,777,780), tertiary amines prepared by chemically combining a monoalkylamine, aralkylamine or ethanolamine with ethylene oxide (see Japanese Patent Publication No. 35697/71), spiroacetal type diamines or reaction products prepared from a spiroacetal type diamine and an oxirane group containing compound (see German Patent Application (OLS) No. 2,343,800) and polyhydric alcohols such as polyethylene glycol or polypropylene glycol, etc., have been used as described hereinafter.
These desensitizers, however, all have an insufficient desensitizing effect, and, particularly, they are not effective on fluoran type couplers such as 3-diethylamino-7-dibenzylaminofluoran. When a coupler is brought into contact with a developer sheet as described above having a desensitizer layer, a developed image often appears with the passage of time, though the developer sheet seems to be perfectly desensitized initially.
Therefore, in the case of applying a densensitizer by printing it was necessary to apply it very thickly. Consequently, it was impossible to increase printing rates because the drying of the printed surface was retarded.
Further, in the case that a desensitizer coated surface was drawn or printed on using a colored ink, the printed or drawn image of the color ink was remarkably faded or blurred if the amount of desensitizer was increased.
In pressure-sensitive copying papers, if a coupler containing microcapsule layer is allowed to stand together with a developer sheet comprising a large amount of developer, the desensitizer swells the walls of the microcapsules to sometimes cause destruction of the microcapsules.